Dicamba: The ‘Time Bomb’ Went Off and No One Was Prepared – DTN

    Each year, DTN publishes our choices for the top 10 ag news stories of the year. Today we continue our rundown with No. 7 how dicamba herbicide captured headlines throughout the 2016 season as acres of crops tolerant to the herbicide were planted without a registered dicamba-based herbicide to use over the top of soybean and cotton crops.

    Dicamba may have been used as a herbicide since the early 1960s, but debacles associated with the new dicamba-tolerant trait known as Xtend kept it fresh in headlines this year.

    In early February 2016, farmers and Monsanto celebrated when China granted import approvals for Roundup Ready 2 Xtend soybeans. The trait technology had been under development by Monsanto for more than a decade and farmers struggling with herbicide-resistant weeds have been clamoring for alternatives.

    Monsanto, DuPont Pioneer and several other licensees decided to commercialize Xtend soybeans following the China announcement, although the trait system lacked a registered dicamba herbicide for use in-season at the time. Monsanto had previously sold Bollgard II XtendFlex cotton varieties in 2015 and continued to do so in 2016.

    Early in the year, companies were hopeful that the Environmental Protection Agency (EPA) would approve dicamba formulations specific to the Xtend trait system in time for the 2016 season. As farmers loaded planters, there were still no pre-plant or in-crop use of dicamba approved for those soybeans and cotton. Some existing dicamba products were labeled for burndown weed control prior to planting a crop, but those formulations remained subject to minimum plant-back restrictions.

    As spring wore on, EPA extended the first 30-day comment period on the new formulations. By May, EPA stated that it would likely issue a final regulatory decision in late summer or early fall 2016 on the new dicamba herbicides — too late for any postemergence use.

    During planting and spray season, seed companies again warned growers that making an in-crop application of any dicamba herbicide product on Xtend soybeans or cotton would be a violation of federal and state law.

    Before planting, DTN began contacting state pesticide regulatory agencies to ask how they would deal with illegal applications. Many were barely aware of the potential situation; others said their limited investigative resources would rely on complaints coming in.

    Dicamba-tolerant soybeans hit another snag as some elevators also alerted growers that they would not accept grain produced from the trait since it did not yet have the necessary European Union (EU) approval. The single events (dicamba and glyphosate) in Roundup Ready 2 Xtend soybeans had been previously approved for import in the EU, but not the stacked product.


    The first reports of off-target and off-label use of dicamba herbicides came in June. “It looks like a bomb went off in some parts of the South,” Ford Baldwin, an independent weed consultant based in Arkansas, told DTN in early July.

    The hotbed for the illegal spraying of dicamba appeared to be in western Tennessee, southeast Missouri and northeast Arkansas. However, there were scattered reports of off-label spraying from other states as well, including some in the Midwest.

    University of Tennessee weed scientist Larry Steckel told DTN the intense onset of PPO resistance in his state set the stage for the problems because farmers had already lost the utility of glyphosate. “When you are planting RR2 Xtend beans and you spray Flexstar and it doesn’t work, you’ve got the option of a disk and replant or doing something off-label. Unfortunately, several folks decided to go ahead and spray dicamba off-label,” Steckel said.

    Dicamba News on AgFax

    Unable to display feed at this time.

    Weed scientists have said that both DMA (Banvel) and DGA (Clarity) formulations of dicamba were used illegally in 2016 and damage came both from physical drift behind the boom and vapor movement. “We’ve sprayed dicamba as a burndown and in small corn over the years, but temperatures are typically cooler when those applications go out,” Steckel said. “Spraying later in the season at warmer temperatures is a different animal. The biggest surprise to me and others was that it [dicamba] moved miles.”

    Temperature inversions are also being blamed for some of the off-target movement onto sensitive crops. Some sensitive crops were hit with drift multiple times, weed scientists said.

    State regulatory agencies began investigating reports of dicamba damage to sensitive soybeans, specialty crops, timber and home landscapes. They soon found themselves overwhelmed by the complaints. Missouri recorded the largest number of dicamba-related complaints — all 124 investigations remained open as of mid-December.

    Farmers with Xtend soybeans growing in the field breathed a sigh of relief in late July when the EU signed off on the trait. The approval for import and food/feed use of Roundup Ready 2 Xtend soybeans into the EU removed an important market access barrier just in time for harvest.

    In October, EPA confirmed that it had executed federal search warrants at several southeastern Missouri locations as part of an investigation into alleged misuse or misapplication of dicamba onto herbicide-tolerant soybeans and cotton.


    The ongoing dicamba tale turned tragic in late October when 55-year-old Monette, Arkansas, farmer Mike Wallace was fatally shot during a physical confrontation with a neighbor that allegedly began over the illegal spraying of dicamba. Wallace was quoted in a Wall Street Journal article in early August expressing concern that as much as 40% of his soybean fields had been damaged by dicamba drift and he had filed a complaint over the situation with Arkansas officials.

    Allan Curtis Jones, 26, of Arbyrd, Missouri, has been charged with first-degree murder and has a Dec. 30 date in Mississippi County District Court. Members of the Wallace family testified before the Arkansas Plant Board in November asking the board to take measures that would stop the damage. Bradley Wallace said his father made numerous calls to the Plant Board during the 2015 and 2016 growing season “hoping to find a helping hand willing to assist in bringing the illegal spraying to an end.”

    He added, “We’ve seen exactly what the old formulations are capable of and there’s not enough research to prove the new formulations will not do the same.”


    In November, the EPA finally registered the first dicamba-based herbicide to use with the Xtend trait. XtendiMax with VaporGrip, a DGA salt-based formulation, contains an additive that Monsanto has said helps reduce volatility over previous DGA formulations by 90%. However, weed scientists were quick to point out they have not had access to the new formulation to confirm the volatility claims and that volatility does nothing to reduce particle drift.

    In December, EPA approved Engenia, a new BAPMA dicamba salt that is said to have a lower volatility profile. DuPont also announced it is licensing a DGA-based herbicide with VaporGrip from Monsanto to be marketed under the trade name FeXapan. Monsanto continued to pursue registration of a glyphosate and dicamba premix herbicide.

    EPA also put farmers on warning by issuing a two-year conditional registration for XtendiMax that included tough drift mitigation measures such as no tank mixing, one specific nozzle, downwind buffers, wind speed and boom height restrictions.

    Some states are also seeking more stringent requirements than the federal XtendiMax label. Mississippi, for example, has proposed to reduce the wind speed allowance to 10 miles per hour (mph), compared to the federal label’s 15 mph. Other states are considering restricted-use herbicide status for the new formulations. On Nov. 21, the Arkansas Plant Board voted to ban all DMA and acid salt formulations, to prohibit the spraying of XtendiMax between April 15 and Sept. 15, to set slightly different buffer requirements for Engenia and to require special applicator education. Those proposals currently sit before the Arkansas governor for consideration. Many states are looking at legislation that would significantly increase fines for growers caught spraying older formulations on Xtend crops.

    As the year wound down, Missouri’s largest peach grower announced he is suing Monsanto over damages from dicamba drift. Attorney Bev Randles told DTN that Bader Farms, of Campbell, Missouri, experienced herbicide damage consistent with dicamba injury to more than 7,000 peach trees in 2015, another 30,000 peach trees in 2016 and some timber.

    Steckel and other weed scientists were urging growers to attend learning sessions on the new trait technology and to take the new spray requirements seriously. “I think if applicators follow the label, they can make Xtend work,” Steckel said. “The question is: Will they? It will only take a few weak links in the chain to cause a lot of issues.

    “We’ve never seen this herbicide applied on a landscape level,” he added. “I’m worried if we don’t do it right, this could be a one-year-and-done technology.”

    Pamela Smith can be reached at

    Follow Pamela Smith on Twitter @PamSmithDTN

    The Latest

    Send press releases to

    View All Events

    [ecs-list-events limit="5" key="start date" order="asc"]
    Send press releases to

    View All Events